At some unknown point during the events of Sengoku Rance, Kakusui was one of several people recruited by the warlord Gumo Danjou to form the Silver Eye Sect. Her skill as a ninja allowed her to achieve a high standing within the group, serving as Danjou's right hand and assassination specialist. Before the group became active, however, Danjou and the majority of its members were killed by the KunoichiSuzume, who had happened to have been fishing near their base at the time. Kakusui managed to avoid being killed due to having been coincidentally away at a Birdman rally at the time when it occurred. After discovering her master and colleagues dead, Kakusui vowed to take revenge on Suzume and Inukai through whatever means possible.

As second in command of the Silver Eye Sect, Kakusui was appointed leader by the remaining members, and the group began working in secret to prepare its revenge against the Iga ninja. Setting up a base in the former headquarters of Momotan, the founder of ninjutsu, and taking out several loans from the merchant Pluepet, the Sect regained a portion of its lost strength and began operating again.

Kakusui is cornered by Suzume when attempting to steal the Decapitation Blade.

Believing herself to be incapable of defeating her nemeses on her own, Kakusui aimed to first assassinate Kentou Kanami, who was training under Inukai at the time, in order to take the legendary Decapitation Blade from her possession to increase her power. When Kakusui infiltrated Iga, she found Kanami seemingly already dead and took the Decapitation Blade from her effortlessly. In actuality, Kanami was playing dead as part of her ninja training, and incorrectly assumed that Kakusui was Inukai, causing her to put forth no resistance. Before she could escape, however, Kakusui was intercepted by Suzume, who quickly overpowered her in a fight. While she managed to escape with her life, Kakusui had alerted Iga to the Silver Eye Sect's reactivation, causing Inukai to send Suzume and Kanami to Momotan's Fortress to take back the Decapitation Blade and crush the organization once and for all.

After returning to her hideout, Kakusui became lost in the elaborate layout of the fortress, and discovered that Suzume and Kanami, aided by the warrior princess Senhime, had already made it to her room long before her. She then attempted to fight the trio but was defeated fairly easily. In a last ditch effort to kill Suzume, Kakusui revealed that she had lined the fortress' walls with hundreds of Puchi Hanny, detonating the building in a suicide attack. The effort failed on all fronts, with both Suzume and Kakusui herself surviving the explosion. While Kakusui immediately began planning her next revenge attempt, she was quickly cornered by Pluepet and forced to sell herself as a slave to him to pay off the debt she had racked up during her previous scheme.

Kakusui is a young woman with pale skin and long black hair kept in a large pony tail. Her red eyes sport dark circles around them, giving her a somewhat rough appearance. Her clothing consists of a sleeveless black dogi and a long, tattered cloak. She wears a single red stocking on her left leg, which is used to hold short swords. When on the job, she prefers to drape her cloak across her entire body, giving her a more sinister appearance and masking her true gender.

Kakusui is a very self-conscious person who struggles to be seen as threatening. She works hard to cultivate an image as a mysterious, dangerous person, but generally fails to come off as anything more than pathetic. She is shown to be quite scatterbrained and clumsy, getting lost in her own hideout, failing to whistle properly when calling her minions, and tripping over her own cloak at various points. She takes herself very seriously, and is prone to breaking out into long speeches about how she will avenge her master, only to be ignored by the people she is talking to. When frustrated, she has a tendency of chastising herself for being useless, suggesting that she has low self-esteem. Despite this, she is highly regarded and loyally followed by her subordinates, with several even having crushes on her.

Kakusui had no choice but to sell herself to Pluepet in order to pay her debt.

Kakusui is incredibly devoted to her deceased lord Gumo Danjou, serving as his loyal ninja while he was still alive and making multiple attempts to avenge him after his death. Her loyalty is best shown during her final attempt at killing Suzume, where she was perfectly willing to blow herself up in order to avenge him. While Danjou's feelings towards her are unknown, his notorious hatred for all ninja suggests that he did not return her respect, and likely saw her as little more than a tool.

Kakusui has sworn to never rest until she has killed both Suzume and Inukai. Despite this, she has no confidence in her ability to do so and makes heavy use of trickery in an attempt to improve her chances. While she considers Suzume to be her fated rival, Suzume doesn't register her as a threat at all and never acts seriously in her presence. Inukai, meanwhile, pities her somewhat due to believing that she is simply another victim of the cycle of revenge, though he still shows no mercy when pursuing her.

Kakusui is a skilled ninja of considerable ability. She was the second in command of the Silver Eye Sect, showing that Gumo Danjou acknowledged her talents despite his hatred of ninja. She is shown to be able to easily disarm Kanami and is substantially stronger than the elite ninja serving in the Silver Eye Sect, suggesting that she is far above average in terms of talent. Her power isn't comparable to truly gifted ninja such as Suzume, however, as she quickly loses when engaged in a straight fight with her.

In combat, Kakusui utilizes a unique fighting style known as "Crane Wing Blade", which incorporates holding a hidden blade in her foot to attack her enemies by surprise with. Through this technique, she was able to gain the upper hand in a fight with Suzume when wielding the Decapitation Blade, showing it to be quite effective in one on one combat. Despite this, as Suzume was being supported by both Kanami and Senhime at the time, Kakusui was still defeated fairly easily.

While she is shown to be highly respected by her followers, Kakusui is untalented as a leader, lacking any skills in management. After taking control of the Silver Eye Sect, she very quickly plunged it into severe debt, and continued to increase it as she unsuccessfully tried to stop Suzume, ultimately resulting in her being forced into slavery by Pluepet to pay it off.